Method of making milling-cutters



F. MULLER.

METHOD OF MAKING MLLLING CUTT'ERS.

APPLICATION FILED LAN. I3, 191.9.

1 348, 302 Patented Aug. 920.

I 5 HEETS-S EE a 0 my F. MULLER.

METHOD OF MAKING MILLIN TTERS. APPLICATION FILED JAN-l 19.

1 348,302, Patented Aug. 3,

5 SH -SHEE F. MULLER.

METHOD OF MAKING'MILLING CUTTERS.

APPLICATION menu". 13, 1919.

1,348,302. Patented Aug. 3; 1920.

5 SHEETSSHEET 5.

auvmxow a czneg IVUNITED STATESSPi-ATENT OFFICE;

FRIEDERICH Mij'LLER, or HARTFORD, coNNnc'riour, ASSIGNOR' o PRATT & WHITNEY COMPANY, or NEW YORK, N. Y., A CORPORATION on NEW J R E 1 METHOD or MAKING MILLING-comings,

Specification of LettersPatentf Patented ling, 3 1920,

Application filed January 13, 1919. Serial No. 270,941.

To all whom it may concern:

Be it known that I, FRIEDERTCH MI'iLLEn, a citizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have invented certain new and useful Improvements in Methods of hIaking Milling-Cutters, of which the following is a specification. I

It is a well known principle in the art of cutting'nietals that the cutting edge of the tool should preferably be inclined with respect to the direction of relative movement so as to effect a shearing cut. This inclination is of advantage in that it improves the cutting'action and it is also of advantage in that it permits the tool to engage the work gradually and with relatively little shock instead of engaging it suddenly with greater shock. This principle has been applied to relieved milling cutters which are of uniform diameter throughout and has also been applied to milling cutters having a uniform taper from one end to the other. These milling cutters have their cutting edges longitudinally inclined'with respect to the axis, the cutting edge usually approximately conforming to a helix Thus each tooth is enabled to engage the work gradually and to effect a shearing cut.

I have applied this principle to accurately made and properly relieved formed or contour cutters. By a formed or contour cutter I mean one in which the diameter varies from end to end'in ways differing froma' uniform taper, the cutter being thus adapted to cut a predetermined contour-other than a straight line; Prior to my invention it had not beendeemed practical or possible to make such cutters with inclinedcutting;

invention set forth in my saidapplication' Serial No. 268,3t9. In accordance with the method disclosed in the first said application, Serial No. 268,350, the cutter is formed by means of a preliminary milling cutter or I a preliminary lathe tool made with aconliminary tool to finish one tooth before engaging the next tooth; In accordance with the method disclosed in the second said application Serial No.248,1 90-I avoid the limitations which are incident to the method set' forth in the-first application; The cutter may have' the forward outer corner of I each tooth overlapping the opposite rear outer corner of the next tooth. The method involves the use of a fine pointed'lathe tool which is guided to follow the desired contour and thus cut the said contour on the cutter. I

The present invention relates to a method somewhat similar to that presented in my last said application, Serial No. 248,190, dif fering, however, in that a relatively broad tool is'used instead of a pointed tools Use is made of the same principle that is used in the method presented in my said appli-- cation Serial No. 268,350. I

As to apart of its subject-matter this application constitutes. a continuation of 'my abandoned application for methods of making milling cutters, Serial No. 248,191, filed August 3rd, 1918.

In order that thevmethod may be clearly understood, I have shown in the accompanyingdrawings a cutter embodying the invention set. forth in the aforesaid application Serial No. 268,349, and I have illustrated two ways in which the method may be practised.v It will be understood, 'however, that the drawings are for illustrative purposes only and are not to be construed as defining or limiting the scope of the invention, the accompanying claims being relied upon for thatpurpose. It will be particularly understood that the contour of the cutter shown has been selected merely byway of example and that any practical contour may be substituted for that illustrated. i

Of the drawings:

Figuresll and 2 are side and end viewsrespectively of the cutter such as may be made in accordance with the invention.

Fig. 3 ma developed fragmentary cross in succeeding. views the angle of inclination termediate "@001 shown sectional view, the section being taken through thebottom of one of the longitudinal grooves along a helicoidal surface such as 33 indicated in Fig. 2.

Figs. 4 and 5 are plan andendviews respectively of a preliminary milling cutter which may be used for forming the shape of the finalcutter shown in Figs. 1 and 2. Fig. 5 shows the cutter in operative relation to an intermediate tool.

Fig. 6'is an enlarged diagrammatic view illustrating certain features of the cutter shown in Figs, 4 aud t).

. Fig. 7 is an enlargedplan view of the. in-

v in Fig. 5 on the same scale as Fig. 6. I

Fig. 8 is a diagrammatic'side view illustrating the intermediate tool in use for cutting a lathe tool,

Fig.9 is an enlarged plan view of the lathe tool on thesamescale as Figs. 6 and 7.

Fig. 10 is'a diagrammatic plan View illustrating the generalmethod that is followed.

Fig. 11 is a diagrammatic plan view illustrating one step of an incorrect method- .A

lathe tool is shown in engagement with a cutter blank. I r

Fig. 12 is an enlarged viewof the lathe tool and'adjacent parts shownin Fig. 11.

. Fig. 13 is a fragmentary front view of the elements shown in Fig. 12. V In this view and of ithecutting faces of the cutter is considerably increased.

- Fig. 1 1 is a diagrammatic cross sectional view. illustrating the. relationship between the lathe tool andv the cutter.

Fi 15 is a View similar to Fig; 11 but showing the lathetool in a differentposition.

Fig. 16 is an. enlarged view similar to Fig: 7 12 but showingthe lathe tool in the position illustrated in Fig..'15.' Y v Fig. 17 is a view similar to Fig. 13 but showingthe lathe tool in trated in Fig. 16. l V

Fig. .18 is a view similar to Fig. 14but showing the lathe tool and the cutter in the position illustrated in Fig. 17.

Figs. 19 to24-are views corresponding respectively to Figs. 12, 13, 14, 16, 17 and 18- the position illus- I tool adaptedto be used for shaping the preillustrating the relationship between the preliminary and final cutters as shown in Fig. 27.

Fig. 29 is a view'similar to Figs. 22 and 27 and showing another relationship between the preliminary and final cutters.

Fig. 30 is a view similar to Figs. 24 and 28,

Fig. 29. i e

I F ig. 31 is a diagrammatic plan view of a machine adapted for. carrying out the method. 7

Fig. 32 is a cross sectional view of the machine illustrated in Fig. 31.

In order that the method involving the invention may be clearly understood, 1 will first describe a cutter such as may be made in accordance therewith; Referring to the drawings, particularly to Figs. 1 and 3 thereof, it will be seen that I have shown acutter l3 which'is shaped to cut a predetermined contour differing from astraight line. 'The cutter is provided with a plurality of generally longitudinal teeth 1 between which are grooves 2, the teeth and grooves being preferably spaced uniformly. The groovesi 2 between the teeth can be ofany usual or preferred depth and shape, as required by the spacing and by'the depth of the-contour to be cut. The front wall 3 of each tooth 1 constitutes the cutting face thereof andthis cutting face is radial or approximately soin order to provide a satisfactory cutting angle. Each cutting face3 is inclined or positioned obliquely so that its longitudinal lines lie at angles'to the axis of the cutter. as shown, the entire teeth 1 are oblique or inclined, and not merely the front cutting faces 3 thereof. Asconcerns the broader Preferably,

phases of the invention, I do not narrowly limit myself in regard to the nature of the inclination ofthe teeth 1 or in regard to the character of the front walls orcutting faces 3, but preferably eachtooth 1 is generally helical in formand eachcutting faceB conforms to a helicoid. As illustrated in Figs. Y

1, and2thehelicoid' is one formed by a gen eratrix following the axis of the cutter and also following a helix on a cylinder concentric with the axis thereof, the helicoid in this case being radial. The character of the helicoid may, however, be varied. The teeth,

and the cutting faces may be inclined in either direction and the degree 'of inclination may be varied as required. I I

' The cutter B may be made for cutting any desired practical contour. The contour may be made up of a'series of straight lines, or a series of circular arcs, or a combination of circular arcs and'straightli'nes, or the contour may consist in whole or in part of noncircular curves. The cutter shown in Figs. 1 and'2 is adapted for cutting the contour shown in Fig. 3, this contour consisting of a straight section lparallel with the axis, a concave section in the form of a circular arc, a straight section 6 inclined with respect to the axis, a concave section 7 in the form of a circular are, a convex section 8 m I the form of an elliptical arc, a concave section 9 in the form of a circular arc, and a straight section 10 parallel with the axis.-

The grooves 2 can be of any usual or preferred depth or shape asrequircd by the spacing and by the depth of the contour.

As illustrated in Fig. 3, each groove 2 has a uniform depth throughout; that is, its bottom is at a. uniform distance from the axis of the cutter.

The outer edge of each cutting face 3-has an outline which is shapedto cut the predetermined contour whenthe cutter isrotated, this outline of the cutting face following the helicoidal surface thereof. All points along the outline must beat their respective correct distances from the center so that,

. tions in angulan position resulting from the warped. or, helicoi dal cutting face. I Preferably the relief lines 11 are maintained in. similar relationship to each other as they I extend backward-and inward,the lines preferably conforming to spirals of Archimedes.

The result is that each toothof the cutter, at any axial plane of intersection, has a dis torted shape, the distortion of shape resulting from the, fact that the successive inward inclined relief lines 11 start at different angular positions because of the inclined or helicoidal cutting face. Notwithstanding this-distortion. in shape at axial planes'of intersection,the outline or effective. contour at the cutting face is correct, as beforestated. Then the relief lines 11 conform to spirals and are maintained in similar relationship as they extend backward and inward, as is preferred, it IS possible to sharpen or grind I the teeth of the cutter on the front cutting tersection similarin form and position to i faces 3 without changing the effective con- I -tour.. The teeth present the same effective contour atisuccessive inclined surfaces of inthe initial cutting faces 3. ,At any surface, back of an initial cutting face 3 and'similar to r the said face, the same effective contour will beffound. Thereforev if the cutter is ground on the front faces to helicoidswhich arethe same asthe helicoids ofthe initial cutting facesthe effective contourwill remain the same.

With a relatively long contour suchas that shown and with the teeth relatively closely spaced, overlapping occurs to a greater or less extent. -The forward outer corner a of each tooth, overlaps the opposite rear outer corner 0 of the next preceding tooth. This overlapping may be even greater than that shown when there isa longer/contour, or when there is a greater degreeof'inc'lination, or'when-the teethare more closely spaced. I

' The present invention relates .to a method of making a cuttersuch as thatset forth and this method will now be described. It will be understood that the preliminary steps of turning the blank and cutting the grooves therein can be carried on in any usual or preferred way, these not of themselves constitutingany part of the invention. The inof shaping'the blank to properly form and v relieve the helical teeth so that they will cut a correct contour.

In my said application Serial No. 248,190 I have described a method involving the use of a narrow lathe tool for-shapingthe'final cutter. While a narrowtoolhas many features of advantage it may sometimes be preferable to use a wider lathe tool such as S shown in Figs. 8 and 9, or. a Wider rotating milling cutter such as .T shown inFigs. 4

and 5.

In practising the method, the tool S or the cutter T is held in operative relationship witha blank B, as shown in F ig. 10, and is fed and guided, preferably toward the left, so as to followthetruecontour 4-10. During the cutting operation the blank is axially rotated by anypreferred means. .The .tool ispreferably held in parallelism while being fed, and the feeding is preferably effected uniformly from one end of. the blank to the other. For guiding the tool there is provided a formerUhaving;exactlvthe predetermined contour to be cut by the cutter B.

Theformer is engaged by a pin Vwhich has the same or approximately the same front outline, as the tool,-the shape of. the pin as shown beingexactly half-round or' semi-circular. The. former pinis connected'with the tool for longitudinal'movementin unison therewith. In order thatthe teeth of the cutter may be properly. relieved, the

tool or cutter is reciprocated toward ,and

from the blank axis in" timed relation to the blank rotation. To enable the tool to properly cutthe relief in accordance with the inclined helicoidal. cutting face the relative timing of the tool reciprocations varied in 90 vention relates particularly to the, method r I 'length'ofthe cutter.

' different positions of'the tool and former pin.

xtetemedies tenth-e longitudinal movejmentof the 6001: In thisway the tool is so Apreliminary milling cutter such as'T may beiis'ed directly to mill 'thejfinal cutter,

and when'alathe' tool'such as S'is-to' be used thesameor a similar milling cutter T is uti in some'respeots siinilar to the method "set forth'in iny' aforesaid cop'endi'ng application Serial No. 268,350. ieferencecan be had to the said -fapplicationf'or details and "for'possible variationsnot hereinset forth.

' The cutter is provided[with teeth 12 havinggrooves between them. :The teeth areso formed asto have a suitablefconvex plane'of intersection pr efer'ably semi ciri-u by dotted lines in]? 6. "The f1*ont'or cutting faces: 1.4" off the teeth 1.2"arelifelicoidal'in, fo'rmQand are inchned iiithe same direction as the cutting faces 3"ef the final cutter."

.Thehelicoidal fac'es'arepreferably constructed with" the "same longitudinal pitch as .ithehelicoi'dal faces 3 of theffinal cutter B.

The cutter T is smaller diameter than the final cutten'BYand therefore the actual 'ini' clinationfof its cutting 'faces' '14 isv somewhat f 5..

less than the inclination of the cutting faces 3"but the cutting facesof 'both' cutters never- """theless. eonform to similar helicoids, that is,

to helicoids having the same longitudinal pitch. "Similarly the cutterfiT 'is'provided with 'thejsame degreeof relief as that of the relief is somewhat"greater; but it neverthe- "less "eorresponds to' similar spirals.

The cutterTiconstructedas shown and described,

hasanfeffective contour shown "by full lines in, Figfli' which different from the true semi-circular contour.

The cutter Tis usedtd form theshape'of" the"aforesaid"lathe'ftool S, 'use' made of an? intermediate tool' 1 VV'. The milling cutter T'is use'dito niillfl the intermediate.

iVltl lOfit relief; it being fed perpendicularly to i l arrow "in"'Fig. 5

. l fThe intermediateitoolflvis used,'as shown" in Fig. 8 ,l forfcutting'the"lathe tool s. The

lii' shapeat an axial such as 6-45, as shown actual angle of torted contour w11icih'ist1ie-samt as'the ef fectiv'efcontouif'ofthe cutter shown by f ull' 'lines iri FigfG; This distorted contour "is illustrated injthe plan View in Fig. 7. 'It \i ill "be obse'r'vedthat thetool W is formed cutting fface 15 immersed by the] face i7'inclined with respect to the cutting face to proizide the "necessary relief. The

tool'VVisset with its cutting face 15 parallel with the cutting face 16 of the tool'S, and

"relative reciprocation isthen effected along lines parallel with the front face 17.

15 of the tool W. This distortedcontour is shown in Fig. .9, the amount of distortion I bein'gfindicated by inclined dot-and-dash lized for making the lathe tool; The cutter i Tiis formed'by following a method which is lines. p g r I will first describe the method involving "the use of the lathe tools. It has already been stated that the Variation in the timing movement "of the tool along the contour.

With ayerynar'row tool it may be assumed that thelcutting point is fixed with respect to the tool and is at 'the'central plane thereof. But with a tool such as S of considerable width, the cutting point will not be always at the center ofthe tool and may beatone side of the other thereof in'accordance with the shape of't'he contour to be cut.

Fig. 11 shows a half-round tool S having a shape exactlythesame as that of the former pinV; In this View the cutting point is at e at the left-hand side of the center.

to different 'positions on one side'and from 'Fig. 1 5 is a similar View and it'shows the cutting point at f attheright-hand side of side to side as the inclination of the contour changes. The variation in the timing of the reclprocating re'lleving movement takes no account of'theshiftin'g of :the cutting point, and it is such that the cutting action is correct when the cutting point is at the center of'the tool, but is not'correct when the cutting point is atone side or the other.

Fig. '12 is an enlargement of a part of Fig. 11, and l ig'f1'3 is a face View showing "the tool S in'the position indicated in Fig. 12, the cutting point being at e. In Fig. 13' "the degree of inclination of the tooth 1 and "the cutting face 3 is considerably increased.

The timing of the reciprocating movements is such-as to bring the tool S into its outer position when the central point of the tool is opposite the cutting edge, as shown by the "full line section in Fig. 14. The dotted line section in Figf-M: is taken through. the point "(and shows that the front face of the tooth starting position until after the frontface of'the tooth has passed. The result is that thetooth is cut with a relief line e "g which is "too high instead'of with a correct relief line 11 having a point but the correct distance from the center of the cutter. The

amount of error measured radially is indi-v cated by 2'. r

Fig. 16'is an enlargement of a part of Fig. 15 and Fig. 17 is a faceviewshowing the tool Sin the position indicated in Fig. 16,

the cutting point being at In Fig.':1"7 the degree of inclination of the tooth 1 and the cutting face 8 is increased asin F ig. 13.- The timing of the reclprocating movementsis such as to bring the tool S into its' outer position when the central point of the'tool is opposite the cutting edge, as shown by the full line section in Fig. 18. The dotted line section in Fig. 18 is taken through they point 7' and shows that the front face of thetooth does not reach the cuttingplane soon enough. The toolcannot start to out until the front face of the tooth reaches it, at which time the tool has moved inward to bring the point f to the positionf. The result is that the tooth is cut with'a relief line' f-j which is too low' instead of'with a correct'relief line 11, having a point It: at the correct distance from the center of the cutter. The amount of error measured radially is indi-' cated by Z.

It will be understood 'that similar errors occur at all positions of thetool except where the cutting point is at the tool center; The errors vary in extent in accordance with Figs. 12, 13, 1 4, 16, 17 and 18, the only dif ference being that the tool S'has been substituted for the tool s". In Figs. '19 and 22 the half-round shape of the tool ,S is shown by dot-and-dash lines. The cutting points 0' and f of the tool S are indicated and also the corres ondin cutting points 6" and f of the too S. It will be-observed that the point e is farther in toward the axis by-the distance 11 thus correcting the error indicated in Fig. 14, and that the point f" is farther out away from the axis by the dis tance Z-thus 'correcting'the error indicated in Fig. 18.

It will be unnecessary to enter into a detailed description of Figs. 19to 24 and it will be suflicient to point out that on ac-. count of the corrected shape of the tool the cutting point e isat the proper position to engage the tooth at the point h and to cut the correct relief line 11 on; the cut:

ter tooth, as shown in Fig. '21. Similarly the cutting point 7" is at the proper position as shown in Fig. 24.

to engage the tooth at the point is and to cut the correct relief line 11 on the cutter tooth,

Under some circumstances, it may be preferable tomill the contour of the cutter To do this I substitute for the lathe tool S. the milling cutter T as shown in Fig. 26. The milling cutter T may be the same as he cutter T already described, but it preferably differs in being providedwith a small correction, as set forth in my said application Serial N 0. 268,350. The cutter T is made with a lathe tool X which is provided at its top cutting face 18 with a concave shape as shown in Fig. 25, which is exactly the same as the convex shape of the former p n V. The lathe tool X is used in a re-' lievi-ng lathe and it is set with its top cutting face in a plane at an angle to a plane through the 'axisofthe cutter, as shown in Fig. 26. lVhen the cutter isbeing formed it is rotated in the direction of the arrow, the tool X being moved in and out, as indicated by the horizontal-arrow, so as to follow the proper relief lines.

Figs. 2' 7,- 28, 29 and correspond respectively to Figs. 19, 21, 22 and 24 but show the milling cutter T substituted for the lathe tool S. Figs. 27 and 29 are to be understood "as showing merely the effective contour of'thegcuttm' T rather than any specific p'artthereof. The milling can be considered as taking place along a plane (Z(Z as indicated. The shape of the teeth of the final cutter 'is determined as they pass the said plane (Z-d- The plane is at an angle to a plane through the axis of the cutter B, but the cor- 1 rection shown in Figs. 25 and 26 compensates for this. The effective contour of the cutter T is therefore the same as the contour of the tool S as shown in Fig. 19. The

operation is exactly the same as already'described in connection with the tool S and repetition of the description is unnecessary.

I do not herein specifically claim the "method involving the use of a preliminary milling cutter directly for milling the final cutter. This method is made the subject of my copending application for methods of making milling cutters, Serial No. 270,942,

filed on even date herewith. V In practising the invention use may be made of a machine in some res 'ects slmilar to that set forth in my copen ingapplicaa tion for relieving machines, Serial No.

286,524. filed March 31, 1919. The machine is not claimed as a part of the present invention, but in order that the method may be more clearly understood I have illustrated diagrammatically in Figs. 31 and 32 the essential parts of a machine for carrying out the method. It will be understood that, so

far as this invention is concerned, the machine construction can be Widely varied. As

illustrated, 19 is a mandrel upon which is carried a cutter blank B. Suitable means are provided for supporting and rotating the Longitu'dinally ,movable along mandrel. ways 20, 20, isa carriage 21 upon which is mounted a transversely movable slide 22. Carried by the slide 22 is an independently movable transverse slide 23 which carries the tool S or the cutter T, the tool S being shown. There is preferably an intermedi-f and thus holdingf thc former pinV always in engagement with the former U. It will be seen that whenthe carriage 21 is moved longitudinally the slide 22 will be caused to move transversely under the guidance of the former, the tool S thus being caused to develop an outline which is exactly the same as that of the former U.

A' cam 26 is splined to a shaft'27 which rotatably mounted on the slide 22. The cam 26 and" the shaft 27 a re bodily movable in accordance with the] transverse movements of the'slide 22. -When the slide 22 moves longitudinally with the carriage 21 the cam 26 moves alongthc shaft, the-shaft; itself bereciprocated.

ing fixed against longitudinal movement.-

Thus the cam 26 partakes of all of the bodily movements of the slide 22. A finger 28 secured tojthe slide 23 engages the cam and a spring 29 is provided for pressing the slide 23 outward, thus'holding the finger 28 against the cam. Suitable means, not fully shown, are provided for rotating the shaft 27 in timed relation with the mandrel 21, the shaft being given one completerotation for each rotation of the blank B. Thus the tool S is In order to effect the aforesaid variationin the timing of the relieving movements, the groove or keyway 30 of the shaft 27 is helical. inform and has' the same degree of inclination, that is, the same longitudinal pitch, as theteeth of the blank B. The result isfthat when the tool S is moved longitudinally of the blank the cam 26 is moved along the shaft 27. On account of the helical keyway the cam not only'par-' takes .of the'normal rotative movement of the shaftbut is given a supplemental rotative movement, this supplemental movement being exactly. correct in; amount tocause the tool, when in its outermostoperative position at each reciprocation, to engage the front edge of a tooth of the cutter. j y

p In operation, aformer is selected having exactly the predetermined contour, and a former pin U is selected which has across sectionalv shape bearing the described relation to that of the tool, S that is to be used, A blank B is put in place, as shown, this blank having previously beenroughed out and grooved in any usual or preferred way. By means of the slide 24 the tool is adjusted into engagement with the blank at its righthand end and the movement of the I machine is started." The blank B rotates and the tool is given a reciprocating movement to effect the relief. By means of the, carriage 21 the tool is fed slowly toward-the left, therotative movement of the blank and inward and outward but, because the cam 26 is movable with the slide, the reciprocating relievingmovements of the tool s are continued without interruption. Inasmuch as the cam26 moves longitudinally along the shaft 27: as the'tool is fed, there'eiproeating andrelieving movements of the tool are slightly accelerated, thus causing the tool to-engage the blank at the proper timesjnotwithsta'nding the inclination ofthe i cutting faces thereof.

The former, U can] have any desired practical contour, no matter how irregular and thus any desired practical contour, no matter howirregular, can be given to the fin ished cutter B. It willbe seen that in accordance with my invention it'is possible specially constructed cutting tools saine tool Soicutter T may be used'lfor' the reciprocating movement of the tool be- 3 ing continued. By means of the former and the former pin, the slide 22 is moved various contours, it being merely necessary to provide formershaving the contours desired for the cutters.

What I claim is; p 1. The herein described methodfof'shap axially rotating a blank having teeth with helicoi'dal front faces,- in prov'iding a former having the'predeterniined conto iirof the final cutter and @COIHPUJHOII former P111 'havin a, fredetermined convex sha e in .b. providing a cutting tool having an effect ve 115 shape different n-om ha of the former pin 7 7 but related thereto in a predetermined.way,i'

and cutting-the contour of," the, relievedf" final milling "cutter by means of the "cutting tool, thetool" being guided-by""the' said former and former pin to develop the pie determined contour'uand being, reciprocate'd;

in timedbut varying relation therotationofthe blank to provide the required 2. The'herein describe'djmethodof sha i i relief.

ing a spirally relieved milling cutter having helicoi'dal cutting faces adapted toi'cu't a pre 7 1 0 5 ing a spirally relieved'millingcutter havdetermined contour other than a straight line, themethod con'sistin" in axially rotating a: blank having 'tee t with helicoidal front faces, in providing a former having the predetermined contour of the final cut-- ter and a companion former pin having a predetermined convex shape, in providing a non-rotary'cutting tool'having a shape difing a spirally relieved milling cutter having helicoidal cutting faces adapted to cut a predetermined contour other than a straight line, the method consisting in axially ro tating a blank having teeth with helicoidal front faces, in providing a former having the predetermined contour of the final cutter and a companion former pin having a predetermined convex shape, insprovidin a cutting tool having an effective shape fferent from that of the former pin, the difference in shape being dependent on the degree of inclination of the cutting faces of the final cutter, and in cutting the contour of the relieved final milling cutter by means of the cutting tool, the tool being guided by the said former and former pin to develop the predetermined contour and be ng reciprocated in timed but varying relation to the rotation of the blank to provide the required relief.

4:. The herein described method of shaping a spirally relieved milling cutter having helicoidal cutting faces adapted'to cut a predetermined contour other than a straight line, the method consisting in axially rotating a blank having teeth with helicoidal front faces, in providing a former having the predetermined contour of the final cutter and a-companion former pin having a predetermined convex shape in providing a cutting tool having an effective shape dif: ferent from that of the former pin, the diffcrence in shape being dependent on the required degree of relief of the teeth of the final cutter. and in cutting the contour of the relieved final milling cutter by means of the cutting tool, the tool being guided by the said former and former pin to develop the predetermined contour and being reciprocated in timed but varying relation to the rotatfion of the blank to provide the required relie r The herein described method of shaping a spirally relieved milling cutter having helicoidal cutting faces adapted to cut a predetel-mined contour other than a straight line,

the method consisting in axially" rotatinga blank having" teeth with helicoidal front faces, informing azpreliminary'cutt'er hav-' mg the predetermined shape at planes of j intersection"transverse to 'thelines of 'cutting and provided with a cutting face with a degree of inclination'the' "same as that'of the helicoidal cutting faces of the final cutter and provided with a degree of relief the same as that of the teeth of the final cutter, in providing a former having the predetermined contour of the final cutter and a companion former pin having the same shape as the said cross sectional shape of the PIG'.

liminary cutter, and in forming the shape of the relieved final milling cutter from the said preliminary cutter, use being made of the said former and former pin to develop the predetermined contour and relative reciprocation being effected in timed but vary ing relation to the rotation of the blank to provide the required relief.

6. The herein described method of shaping a spirally relieved milling cutter having helicoidal cutting faces adapted to cut a re- ,determined contour other than a straight line, the method consisting in axially ro- 4 ting a blank having teeth with helicoidal front faces, in forming a preliminary milling cutter having a predetermined shape at axial planes of intersection and having its teeth provided with helicoidal cutting faceswith a longitudinal pitch the same as that of the helicoidal cutting faces of the final cutter and provided with a degree of spiral relief ihe same as that of the teeth of the final cutter, in providing a former having the predetermined contour of the final cutter and a companion former pin having the same shape as the said cross sectional shape of the prel minary cutter, and in forming the shape of the relieved final milling cutter from the said preliminary cutter, use being made of the said former and former pinto develop the predetermined contourand relative reciprocation being effected in timed but varying relation to the rotation of the blankto provide the required relief.

7 The herein described method of shaping a spirally relieved milling cutter having helicoidal cutting faces adapted to cut a predetermined contour other than a straight line, the method consisting in axially rotating a blank having teeth with helicoidal front faces, in forming a preliminary milling cutter having a predetermined concave shape at axial planes of intersection and having its Q1001 with thepreliminary milling. cutter, in the said former and former pin to vdevelop providing h fermer having the predeter- Ule prec leterlnined contour and being i'ecip- 1O mined contour ofthe-final cutter and a com- K'OCELtGdiILfiiHIQd but varying relation to the pinion former fpin having the same shape smtzxtiehof the blmk to provide the required as the ea'id c rossseetionalshape of the prerelief. I f I 1 V V limina 'ry cutter, ,end ihcutting the contour In. tee timony whereof I heretlo :rHix my 0f "the relieved fi'nz l milling cutter by means signature, I 7

of the eutt i ng tool, the tool being guided by I FRIEDERICH MULLER. 

